Gun Muzzle Research Articles

Structure and mechanical properties of boron carbide coatings formed by electromagnetically accelerated plasma spraying

Structural and mechanical properties are investigated on thick boron carbide (B 4C) coatings, which are formed onto stainless steel substrates by using an electromagnetically accelerated plasma spraying. Hardness, porosity and surface roughness of the coatings show dependences on both the size of raw powder and the substrates distance. Within the coating conditions using two different sized raw powders; 30±10 μm and less than 10 μm in diameters, and different substrates distances ranging from 10 to 50 mm from the gun muzzle, smaller particle and longer substrates distance are found to be more effective in forming a coating with uniform hardness, low porosity and smooth surface. Results of Raman spectroscopy and X-ray diffraction suggest that the crystallite size of original raw B 4C powder is significantly reduced during the process of coating formation.

Bifurcation and solitary solution of a transient temperature field along axis of gun muzzle

Based on non-equilibrium thermodynamic theory, a temperature field model of gun muzzle is setup. We obtain not only a solitary solution, but also a bifurcation solution. The physical picture of the solutions is corresponding to the center flame and secondary flame of the gun muzzle.

Measurements of Gun Tube Motion and Muzzle Pointing Error of Main Battle Tanks

Beginning in 1990, the US Army Aberdeen Test Center (ATC) began testing a prototype cannon mounted in a non-armored turret fitted to an M1A1 Abrams tank chassis. The cannon design incorporated a longer gun tube as a means to increase projectile velocity. A significant increase in projectile impact dispersion was measured early in the test program. Through investigative efforts, the cause of the error was linked to the increased dynamic bending or flexure of the longer tube observed while the vehicle was moving. Research and investigative work was conducted through a collaborative effort with the US Army Research Laboratory, Benet Laboratory, Project Manager – Tank Main Armament Systems, US Army Research and Engineering Center, and Cadillac Gage Textron Inc. New test methods, instrumentation, data analysis procedures, and stabilization control design resulted through this series of investigations into the dynamic tube flexure error source. Through this joint research, improvements in tank fire control design have been developed to improve delivery accuracy. This paper discusses the instrumentation implemented, methods applied, and analysis procedures used to characterize the tube flexure during dynamic tests of a main battle tank and the relationship between gun pointing error and muzzle pointing error.

WC–Co coatings deposited by the electro-thermal chemical spray method

A novel thermal spray technology — an electro-thermal chemical spray (ETCS) for producing hard coatings is presented. The experimental coating apparatus consists of a machine gun barrel, a cartridge containing the coating material in powder form, a solid propellant, and a plasma ignition system. The plasma ignition system produces plasma in pulsed mode to ignite the solid propellant. On ignition, the drag force exerted by the combustion gases accelerates the powder particles towards the substrate. Using the ETCS technique, the process of single-shot WC–Co coating deposition on stainless steel substrate was studied. The influence of process parameters (plasma energy, mass of the solid propellant and the coated powder, distance between the gun muzzle and the substrate) on the coating structure and some of its properties were investigated. It was shown that ECTS technique effectively deposited the WC–Co coating with deposition thicknesses of 100–200 μm per shot, while deposition yield of ∼70% was attained. The WC–Co coatings consisted of carbide particles distributed in amorphous matrix. The powder particle velocity was found to depend on the solid propellant mass and was weakly dependent on the plasma energy, while the particle processing temperature was strongly dependent on the plasma energy and almost independent of the solid propellant mass. Whilst increasing the solid propellant mass from 5 to 7 g, the deposition rate and yield correspondingly increased. When increasing the plasma energy, the temperature of the powder particles increased, the average carbide particle size decreased and their shape became more rounded. The deposition yield and microhardness at first increased and then achieved saturation by increasing the plasma energy.

Generalization of the muzzle wave similarity rules

The present paper describes an improvement of the muzzle wave similarity that permits treatment to unsteady and non sonic gun muzzle conditions. The revised formulation of the similarity is capable of characterizing the muzzle wave propagation even for significant variation of the muzzle conditions during the life time of the wave. Suitable scaling parameters are selected and tested yielding appropriate similarity rules at a significantly reduced number of tests whose applicability is confirmed by experimental data and comparison to an analytical theory.

COMPUTATION OF HIGH-SPEED REACTING FLOW FOR GUN PROPULSION APPLICATIONS

The launch cycle of a conventional gun system is simulated using a computational fluid dynamics code that has been developed as a design code for gun muzzle devices. A primary phenomenon of interest is the blast overpressures generated by the gun. The governing equations, which include both fluid dynamics and chemical processes, are solved to predict the peak pressures in the field exterior to the gun. A finite rate chemistry model to simulate reactions is implemented to assess the effects of reactions on the blast overpressures. The physical models and the solution algorithm are discussed with emphasis on accuracy and efficiency. Simulations for both large- and small-caliber guns are carried out and compared with experimental data to ascertain the utility of the design code. Computations prove the reaction processes are key in determining the overpressure levels throughout the field.

Integrated launch package performance in the cannon-caliber launcher

The Cannon-Caliber Electromagnetic Gun (CCEMG) Program is a major effort toward proving the viability of electromagnetic weapons for future use by the Armed Forces. The effort is focused on the successful, system-designed integration of several major components. Crucial to the success of the program are the operational characteristics of the launcher and the integrated launch package (ILP). This paper addresses the launch and flight characteristics, accuracy, and terminal performance of the ILP and subprojectile. The results presented here represent the first known experimental assessment of these parameters obtained from electric gun firings of a tactical flight body over realistic ranges. To date, 39 shots have been fired using a 1.6-MJ capacitor bank located at the U.S. Army Research Laboratory (ARL). A wide variety of instrumentation was incorporated to survey transitional, free-flight, and terminal ballistic regimes from the gun muzzle to target impact 222 m downrange. Free-flight aerodynamic data indicated that the round has adequate in-flight stability. Round-to-round dispersion was computed over a wide range of launch velocities based on downrange impact locations and was used to provide estimates of the dispersion at the design launch velocity of 1,850 m/s. A detailed analysis of the transitional ballistic process has been performed to quantify the various contributors to the total launch disturbance. The results indicated that the sabot/armature discard contributes equally with the aerodynamic jump toward target impact dispersion and increases with launch velocity. For the current launcher configuration, the variability of the discard process Is oriented in the vertical direction. Finally, impact data on armor were limited but nonetheless indicate the round is capable of meeting the CCEMG system requirements.

Plastic Guidance Fins for Long Rod Projectiles .

Projectile tail fins on long rod kinetic energy (KE) penetrators serve the same purpose as fletchings (feathers) on an arrow, namely, they help align the projectile axis with its velocity vector. This reduces the projectile's yaw and hence reduces its aerodynamic drag. In addition, a low yaw angle at target impact helps to maximise the projectile's target penetration. It is typical for projectiles to exit the gun muzzle and enter free flight at some ndn-zero yaw angle. Aerodynamic forces acting on yawed tail fins create a stabilising torque about the projectile's centre of gravity (CG). This torque can be increased by making the fin material lighter. Most conventional long rod penetrators fired from high performance guns have tail fins made from aluminium. However, aluminium can undergo catastrophic oxidation (rapid burning) in-bore. Coating aluminium with Al/sub 2/O/sub 3/ {hardcoat) prevents ignition of the substrate, provided solid propellant grain impacts do not chip the brittle hardcoat off the surface. Plastic is lighter than aluminium and less exothermic when oxidized. Therefore, other factors aside, it is conceivable that plastic fins could increase projectile stability while incurring less thermal erosion than aluminium. However, thermal loads are not the only concern when considering plastic as an alternative tail fin material. The mechanical strength of plastic is also a critical factor. This paper discusses some of the successes and failures of plastic fins, at least relatively thin fins, for use as KE stabilisers.

Biological effects of weak blast waves and safety limits for internal organ injury in the human body.

One hundred and seventeen adult sheep of both sexes, each weighing 15.2-42.4 kg, were used for this study. The purpose of this study was to investigate the relationship of the physical parameters of the waves to internal organ injury by exposing sheep to weak blast waves in TNT (trinitrotoluene) explosions, biological shock tube, and gun muzzle blasts. The results showed that the organ most sensitive to the TNT explosion was the lungs, whereas the upper respiratory tract was most sensitive to muzzle blast waves. The injury thresholds of overpressure were 29.0, 29.5, and 41.2 kPa for upper respiratory tract, lungs, and gastrointestinal tract respectively at a single exposure. Repeated exposure to 60 blasts reduced the injury threshold of the internal organs. The injury thresholds for upper respiratory tract, lungs, and gastrointestinal tract were 21.0, 18.0, and 40.4 kPa, respectively. The duration of overpressure of weak blast waves was 2.4-4.2 milliseconds, which did not significantly affect the severity of injury. The safety limits of weak blast waves to internal organ injury of human body were as follows: Ps = 37-3Ln.Tc.N/4(Tc.N < or = 1000) and Ps = 20.4(Tc.N > 1000). The results suggest that repeated exposures decrease the injury threshold of the internal organs. The safety limits proposed could protect 90% of the exposed population against internal organ injury caused by weak blast waves.

Experiments with the Green Farm electric gun facility

The design and construction of a major electric gun facility at Green Farm in San Diego is described. The facility is driven by an 11 kV 32 MJ capacitor bank, arranged in 4 MJ modules that can be independently triggered to provide a choice of pulse shapes. The bank has powered a variety of EM and ET guns, including an 8-meter Single Shot Rail gun and a modified 5-inch Naval gun. World record high energy and high velocity shots have been achieved. The highest rail gun muzzle energy was 8.6 MJ and the highest muzzle velocity was 4.3 km/s with a plasma driven projectile of 0.64 kg, corresponding to a muzzle energy of 6 MJ. Intact projectile launch and flight was confirmed by high speed (8000 frames/sec.) photography and flash X-rays. >

Nonaerodynamic sabot stripper for research gas gun

A nonaerodynamic sabot stripper has been designed and implemented for use with a 40.00-mm smooth bore research gas gun. The stripper consists of several metal parts to stop and contain the sabot while allowing the carried object to pass unhindered through it. The single-piece sabot is stopped by impacting replaceable layers of 19-mm-thick aluminum and steel plates and 3.2-mm-thick rubber sheets. The metal plates and rubber sheets have 25.4- and 31.8-mm diam holes, respectively, for passage of the carried object. The sabot stripper is located 230 mm from the muzzle of the gas gun and is aligned before each shot using a special metal fixture that is inserted into the gun muzzle. Cubes measuring 12.7 mm have been launched in a flat-faced orientation. Targets consisting of 76.2 mm×76.2 mm plates of various thicknesses are positioned in an assembly that attaches to the sabot stripper and is located 57 mm behind it. The velocity range for the experiments was from 0.61 to 0.94 km/s.

Death Investigation After the Destruction of Evidence

Unavailable in the literature is any reference to an investigation of death after evidence has been destroyed. In this presentation two firearms and the bullet were melted after the death was certified as a suicide. A team of investigators conducted a psychological autopsy as well as shot patterns to determine the distance from the gun muzzle to the head to determine whether or not the wound was a contact type. The resolution of the case is discussed and the factor of local politics and case prominence in the media is reviewed.

Effect of electrical/chemical energy input on the Interior Ballistics of an Electrothermal Chemical Gun

AbstractRecent studies have clearly indicated that an electothermal chemical (ETC) gun provides many advantages over solid and liquid propellant guns. However, the interior ballistic process of an ETC gun has not yet been fully investigated. Specifically, the effects of the energy ratio between the electrical and chemical energy input on gun performance is not well understood. Nor is it known exactly how chemical energy is converted to propulsive energy during the ETC gun event. In view of this, a comprehensive theoretical model taking into full account electrical/chemical energy input, liquid entrainment process, distribution of dispersed droplets, and liquid propellant combustion, is developed to simulate the interior ballistics of an ETC gun. Governing equations are formulated from first principles for five different regions, including the gas phase (i.e., Taylor cavity), working fluid (i.e., liquid propellant), dispersed droplets, projectile, and plasma generation cartridge (PGC). Various energy ratios with two different PFN discharge characteristics are employed to evaluate ETC gun performance. Results indicate that the gun champer pressure, muzzle velocity, and ballistic efficiency depend strongly on the energy ratio. The electrical energy input and chemical energy release processes show unequal influence on the gun performance over different stages of ETC gun event. The predicted time history of the breech presure is compared with the measured breech pressur available in the literature. The results show that shapes of the breech pressure‐time traces and values of the peak pressure predicted by the present model agree reasonably well with the experimental data.

Theoretical modeling of the interior ballistic processes in an electrothermal chemical gun

A comprehensive theoretical model has been developed to describe the interior ballistic processes in an electrothermal chemical (ETC) gun. The model, which takes into account the plasma/working fluid interaction, predicts transient and spatial variations of the gun chamber pressure, instantaneous projectile motion, and gun muzzle velocity. A complete set of governing equations is derived from first principles of physics, and the governing system is solved by an implicit finite difference scheme. Two sets of pulse-forming network (PFN) discharge curves, with various peak power times and total discharge times; are employed to study the ETC gun performance. The numerical results show that a ballistic efficiency of more than 13% can be achieved for an exothermic working fluid (C8H18/H2O2). The breech pressure and projectile-base pressure exhibit double peaks during the ballistic cycle. The first peak is due to the initial discharge of a plasma jet into the gun chamber, whereas the second peak is the result of vigorous interactions between the plasma jet and the working fluid. The calculated maximum breech pressure is on the order of 400 MPa, and a typical muzzle velocity is on the order of 2 km/s. Comparison of present numerical results with limited available experimental data is made and found to be good.

Device for silencing firearms and cannon

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Measurement of in-flight base pressure on an artillery-fired projectile

T HE in-flight base pressure has been measured on conventionally fired artillery projectiles. No previous successful effort for such measurements and projectiles is apparent. A passively actuated base-sealing mechanism provided protection to the sensitive base-pressure instrumentation prior to gun muzzle exit and was released after exit to allow base-pressure sensing in flight. Comparisons are made of flight measurements with base-pressure data from wind-tunnel testing.

Gun Muzzle Blast and Flash

AbstractGun muzzle blast and flash phenomena are of importance since they are associated with the formation of large overpressures and intense muzzle flash. About 30% of the chemical energy released from the propellant used in a conventional gun is converted into kinetic energy of the projectile. The remaining energy is mainly contained in the propellant gas‐particle mixture which escapes from the muzzle of the gun in a few milliseconds. The sudden discharge produces a blast wave because of the rapid displacement of air originally surrounding the gun. In addition, these gases are generally fuel‐rich and mix with air turbulently entrained from the surroundings. Combustion of this mixture causes gun muzzle flash, usually associated with the formation of a secondary blast wave. The design of solid propellant charges, gun performance, muzzle attachments and chemical flash suppressants is guided by the need to keep the above hazards to safe limits. In this paper, blast and flash phenomena are characterized using data of recent investigations and showing illustrative examples of their development.

Experimental Results from SHIVA Star Vacuum Inductive Store/Plasma Flow Switch Drven Implosions

Using a 1313-μF, 3-nH, 120-kV, 9.4-MJ SHIVA Star capacitor bank, we have performed vacuum inductive store/plasma flow switch (PFS) driven implosions of low mass (200-400 μg/cm2) cylindrical foil liners of 2-cm height and 5-cm radius. This technique employs a coaxial discharge through a plasma armature, which stores magnetic energy over 3-4 μs and rapidly switches it to an imploding load as the plasma armature exits the coaxial gun muzzle. The current transferred to the load by the PFS has a rise time of less than 0.2 μs. With 5-MJ stored energy, we have driven fast liner implosions with a current of over 9 MA, obtaining an isotropic equivalent 2.7-TW 0.5-MJ X-ray yield.

A new hypervelocity shotgun

This paper presents a technique for launching multiple, hypervelocity projectiles in a predictable pattern. The technique has been successfully applied to collections of 4–42 projectiles launched at velocities of 2 to 5 km/s. The projectile dispersion is obtained by impairing a pre-determined radial impulse to the collection of projectiles as the sabot exits the gun muzzle.

Flow Field Measurements of an Unsteady Reacting Muzzle Exhaust Flow

The events associated with the discharge of a 20-mm caliber weapon have been examined in detail in order to identify and understand important features of the reacting gun muzzle flow field. The diagnostics applied involves shadowgraph and Schlieren photography, invasive pressure probes, spectroscopy for temperature measurements and Laser-Doppler velocimetry for velocity measurements. Emphasis has been on velocity measurements using two setups to determine both the axial and lateral velocity components throughout the muzzle flow field. The data clearly demonstrate the complexity of the processes involved in the unsteady flow expansion of the gun muzzle exhaust flow.